1. Field of the Invention
The present invention relates to an operating apparatus for a clean room for operating a member performing a linear movement under a clean environment.
2. Description of the Prior Art
In a precision positioning system such as an XY table or the like used in an exposure apparatus, a wire bonder, a scanner, etc., an operating apparatus comprising a ball screw apparatus and a linear movement guiding mechanism or the like are utilized in order to insure a linear movement or a positioning of a member to be operated with high accuracy. On the other hand, for example, in the fields of semiconductor manufacturing technology or the like in which such a precision positioning system is utilized, the existence of very minute particles having a size equal to or smaller than the order of micrometer causes a problem. Accordingly, the positioning system itself is operated under a clean environment such as a clean room in which the concentration of suspended minute particles is controlled at a predetermined level. However, powders produced by wear, and minute particles of lubricant or the like (hereinafter referred to as dust) are produced from a moving part of an operating apparatus, such as a ball screw apparatus and a linear movement guiding mechanism which constitute a precision positioning system. In order to prevent contamination of a clean environment to be maintained at a predetermined dust level due to the dust produced from the operating apparatus itself, an operating apparatus for a clean room has been required which is provided with a device for sucking and removing dust produced within the operating apparatus.
A prior art duct preventing measure for the moving part of such an operating apparatus as mentioned above is disclosed for example, in Japanese Patent Laid-Open Publication No. 62-184277. In this dust preventing measure, a bearing of a driving rotary shaft (ball screw shaft) and a nut which constitute moving part to be protected against dust are enclosed by a sealing member. A vacuum suction port is formed in the sealing member for evacuating to vacuum the inside space enclosed by the sealing member.
However, in such a prior art dust preventing structure where the moving part is enclosed by a sealing member provided with a vacuum suction port, the dust preventing structure is complicated.
Furthermore, no measure is provided for lubrication of the moving part as is generally employed, not only is the effect of vacuum evacuation degraded, but excessive grease produces dust and becomes a contamination source. Accordingly, in order to reduce the dust, it is necessary to control the amount of the grease attached onto the moving part. On the other hand, if the amount of coating is too small, the durability of the moving part will be degraded and noise will be increased. Moreover, the production of the dust is correlated with the rotation speed of the screw shaft and, even when the amount of coating is decreased, the amount of dust produced will not be decreased straight forwardly.
Furthermore, in order to evacuate the moving part, it is necessary to attach an evacuation tube to the vacuum suction port and to connect the evacuation tube to an evacuation device. In this case, since the moving part must be moved linearly with high accuracy, it is necessary to take into consideration the movement of the evacuation tube following the movement of the moving part.
Moreover, in order to insure the quality of products, it is important to take a measure so that the starting of the operating apparatus is performed only when the level in the clean room is in a prescribed range.